Motorcycle Repair: battery charging at idle, yamaha 650 v star, amp output

Question
I have heard several times that my 2001 Yamaha 650 V Star does not charge the battery when idling, that the RPMs have to be at hwy speed to charge the battery. Is this true? If so, is it generally true for all Yamahas or just smaller ones?

Answer
Hello Anne,

On the average most motorcycle charging systems
are just designed to maintain a previously charged
battery. This means they can keep a good battery
charged but cannot charge a low battery.

The charging rate increases with the engines RPM or
speed. At idle the charge is very low so if you have
a faulty or half-dead battery it cannot cope.

If you only ride occasionally it is a good idea
to use a maintenance charger on your bike.
This keeps the battery up while it is parked.

It will charge a higher rate while the engine is
running higher speed like highway riding but around
town they tend to break even at best.

The reason the charging systems are weak is because
of the drag and power loss associated with
using a powerful alternator.
This would reduce power and fuel mileage for the owner.
Also more powerful equipment adds weight to the bike.
A car can handle this added drag and weight but
a bike generally cannot.

The smaller the engine the weaker the charging system
generally is due to the above reasons.

If you only ride occasionally around town then
you need to give your battery a maintenance charge
to keep it fully charged.

This is common to all bikes not just Yamaha.
The added drain of steady lights on is also a factor
for some areas. The batteries are smaller on bikes
and have to work very hard to keep up with added
accessories like heated grips or GPS units etc.

Have your mechanic install some wires
on your bike that you can easily attach a small battery
charger to and you will have no problems
with a dead battery.

The maintenance chargers are very low amperage,
about 1 amp output. Do not use an auto
charger as they can overheat the battery and
damage it.

A search online should turn up some low amperage
chargers for motorcycles.

http://www.amazon.com/Battery-Tender-021-0123-Junior-Charger/dp/B000CITK8S/


Luck!
Wayne S.
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